FBI Director James Comey told a congressional hearing this week that he is taking the threat to election systems "extraordinarily seriously"

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Election systems in more than 20 states have been targeted in hacking attempts — far more than had been previously acknowledged — a senior Department of Homeland Security official told NBC News Thursday.

The "attempted intrusions" targeted online systems like registration databases, not the actual voting or tabulation machines that will be used on Election Day. The official described much of the activity as "people poking at the systems to see if they are vulnerable."

And intelligence officials tell NBC News there is now "no doubt" the Russian government is trying to influence the election.

FBI Director James Comey told a congressional hearing this week that he is taking the threat to election systems "extraordinarily seriously," and urged states "to make sure that their deadbolts are thrown and their locks are on."